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Tinnitus and the Hippocampus

Tinnitus and the Hippocampus

Salvi et al (2011) note that approximately 12 to 14 percent of adults perceive tinnitus, as do some 12 to 37 percent of children, and for people with hearing loss the rate of tinnitus can be much higher. Approximately 1 percent of all tinnitus patients suffer debilitating tinnitus requiring treatment or intervention.

As tinnitus is often associated with sensorineural hearing loss, it’s easy to presume the cochlea is responsible for tinnitus. However, studies with Positron Emission Tomography (PET) have identified regions within the auditory cortex, the medial geniculate body, and the hippocampus, which demonstrated increased activation when tinnitus was volitionally increased via oral-facial movements in four selected patients. Of note, Salvi et al report that approximately two-thirds of all tinnitus patients may be able to modulate their tinnitus through volitional activity.

The authors note that the hippocampus is a major site of neurogenesis in the brain and imaging studies show decreased grey matter in the hippocampus (the hippocampus is associated with mood, memory, and spatial navigation) in patients with tinnitus. In lab animals, unilateral noise exposure (resulting in deafness) suppressed neurogenesis in the hippocampus and led to memory impairment. Salvi et al report peripheral damage can/does lead to neuroplastic changes in the central nervous system that may produce phantom auditory sensations (i.e., tinnitus).